GT10 on a Worcester Bosch Greenstore ground source heat pump: HTF in under limit T10 (GT10)
Short answer
On a Worcester Bosch heat pump, GT10 means: HTF in under limit T10 (GT10). The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: HTF in under limit T10 (GT10).
Part involved: T10 collector in.
When it shows: HTF in under limit T10 (GT10).
Likely causes:
- Temporary low HTF temperature; too low collector flow (filter); minimum HTF temperature set too low.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Press Ackn. on the control panel; heat pump restarts within 15 minutes if there is demand. Some causes need a reset button/MCB on the heat pump (engineer).
What you can check
- Read and note the full alarm text and code in brackets shown on the controller and pass it to your installer.
- Press the Ackn. button once as the manual describes (manual: no risk in resetting an alarm); contact technical support if the alarm repeats.
What the engineer will check
- Check collector filter and settings; monitor.
Who to ask for: ground source heat pump engineer.
Certification: F-gas certification for refrigerant circuit; competent person for electrical work.
What you might notice
What owners and engineers report
3 owner and engineer reports mention this.
- No heating on the Greenstore ground source heat pump (original, System & Combi): 2 reports
- Stops working in very cold weather on the Greenstore ground source heat pump (original, System & Combi): 1 report
Sources
- Worcester Greenstore 6/7/9/11 kW System Installation, Commissioning & Servicing ↗ · 8-716-112-860 Issue c · page 38 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026